It is easier to calculate triple integrals in spherical coordinates when the region of integration \(U\) is a ball (or some portion of it) and/or when the integrand is a kind of \(f\left( {{x^2} + {y^2} + {z^2}} \right).\)

It is sometimes more convenient to use so-called generalized spherical coordinates, related to the Cartesian coordinates by the formulas

As the region \(U\) is a ball and the integrand is expressed by a function depending on \(f\left( {{x^2} + {y^2} + {z^2}} \right),\) we can convert the triple integral to spherical coordinates. Make the substitution: